Is this the cause of P21’s dodgy wheel?

Up close to P21’s back right wheel encoder

P21 has had a dicky back wheel since it fell off the roof during filming of the Obstacle Course for PiWars at Home. The motor runs, but the speed is not well controlled, so I assume the problem is related to the encoder.

After the competiton I dismantled the back axle, reseated the connectors, and all seemed to be fine again… for a while.

But recently I’ve been testing a new game for the Sidmouth Science Festival and was frustrated to see that the robot was quite unreliable when aligning on the game pieces. I set to re-tuning the vision system, because that’s always the source of any problems, isn’t it? But this time that didn’t really help.

Finally I realised the robot was sometimes dragging it’s back wheel. I dismantled the back axle again (which is too fiddly and frustrating) and removed the motor.

I see that one of the encoder Hall sensors is leaning out from the magnetic wheel on the motor; see above. Hopefully this is the real source of the problem. I suppose this is due to the fall, but it’s hard to see how.

My plan is to re-print the lower half of the back axle (since it is damaged), re-align the Hall sensor, then put the whole thing back together… But I think I will swap the offending motor with one of the front ones; I really dislike rebuilding the back axle!

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